fix(daemon): present a captured engine's stdout as a pseudo-terminal - #245
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September 25, 2026 04:36
…minal The serve view and the daemon capture the engine's output to a log file, so an engine that gates terminal-only output on stdout being a terminal llama.cpp's model download progress among them produces none of it. The proposal presents the captured engine's stdout as a pseudo-terminal and records redrawing lines as their state.
llama.cpp prints a download's progress only when stdout is a terminal, so under the capture — stdout pointed at the log file — a model download is silent. The pseudo-terminal makes the engine produce the output, and a pump normalises the terminal stream into the log's lines: a redrawing line recorded as its state, first and final always and a further distinct state at most once per two seconds, no escape sequences reaching the log.
An engine that moves onto a line it has already written and writes there without a carriage return rewrites the line the way the terminal shows it; the normaliser was extending the content the line held. The move now settles the state the line draws, and the next write starts a new state of the line. The change also closes the package's remaining coverage gaps: the escape sequences the engines may send, the no-pseudo-terminal fallback, the pump's end-of-stream drain, and the supervisor's refused starts.
The maintainer internals gains the capture's rationale: the normaliser's line model and the rules a 'simplification' would break, the NO_COLOR rule, and the fallback the tests keep alive.
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A model download is silent in the engine log, because the engine only draws its progress to a terminal.
Summary
NO_COLOR=1so its log lines do not reach the file coloured through the stderr pathserveandserve --apiforward the engine's output byte-for-byte as before: no pseudo-terminal, no normaliser, noNO_COLORImplementation details
The normaliser (
internal/daemon/ptylog.go) keeps the terminal's lines as a column and records the states of the ones the engine redraws, rather than emulating a screen. The engine's up-down cursor dance is part of each redraw, so a cursor move moves the drawing between the column's lines and never ends one; a state's replacement is deferred to the next text byte; and a half-rate tick records a pending state on every line, because a bar's last state outlives the engine's move off its line. The pump always drains the master so the engine can never wedge on a full terminal, and the log file closes only after the pump's final record.The change is specified in
openspec/changes/engine-pty-log-capture/and its rationale indocs/maintainer/internals.md.Fixes #226